Hello

I need to move a heap of pptp tunnels to a new server at another location.

This will bring my routing table size to around 3000

Is this an issue?

Thanks

not sure about mikrotik specific issues (probably yes) but in general - you need to re-think your network design... 3000 routes is way beyond "healthy" network.
Why would you need 3000 ospf networks? Can't you divide OSPF domain into areas and do some summarizing?